Aberrant glycosylation is a typical hallmark of cancer cells. Carbohydrate tumor antigens on glycoproteins and glycolipids are therefore targets for active and passive immunotherapy. These highly abundant antigens are de novo expressed or upregulated due to changes in the complex glycosylation apparatus of tumor cells. Various lipid or protein bound carbohydrate tumor antigens are described, e.g. GM2, GD2, GD3, fucosylated GM1, Globo H, LeY and the mucin core structures Tn, Sialyl-Tn and the Thomson Friedenreich antigen.
Thomsen-Friedenreich antigen (TF) is a known carbohydrate structure described as a tumor antigen in a series of reports. TF exists in two forms, TF alpha and TF beta, which can be linked to proteins or glycolipids.
Core-1 is the disaccharide GalB 1-3 GaINAc, which is O-glycosidically linked in an alpha-anomeric configuration to the hydroxy amino acids serine or threonine of proteins in carcinoma cells. Core-1 corresponds to the TF alpha structure of Thomsen-Friedenreich and is linked only to proteins on tumors. Hence, the terms Core-1 and Thomsen-Friedenreich do not necessarily refer to identical structures.
The Core-1 antigen is masked by other carbohydrate components in healthy and benign-diseased tissue but uncovered in a majority of carcinomas and in some non-epithelial malignancies. Therefore, the core-1 antigen is a specific pancarcinoma antigen (see FIG. 20 for illustration).
Core-1 is an important tumor antigen. Core-1 is expressed on over 60% of primary colon carcinomas and over 90% of liver metastases from colon cancer as well as on the majority of the carcinomas of other major indications including breast, lung, ovarian, prostate, and other gastrointestinal cancers such as gastric, and pancreatic carcinomas. Core-1 is an independent prognostic marker for patients with colon carcinomas, the mortality rate increases and the medium survival decreases in accordance with the increasing intensity of Core-1 expression. The development of liver metastases correlates with the expression of Core-1. Patients with Core-1 positive primary carcinomas develop liver metastases in nearly 60% of the cases, while the risk for liver metastasis with Core-1-negative tumours is significantly lower (less than 20%). Besides mediating metastasis into the liver Core-1 may also playa role in the metastasis via the endothelium.
The exceptionally high pan-carcinomic specificity, prognostic relevance and direct involvement in liver metastasis render Thomsen-Friedenreich and particularly Core-1 a prime target for cancer immunotherapy.
There were attempts to provide a therapy approach based on Thomsen-Friedenreich. E.g. Shigoeka et al (1999) describe the inhibition of liver metastasis from neuramidase treated Colon 26 cells by an anti-Thomsen-Friedenreich specific monoclonal antibody in a mouse model. However, due to the difficulties in generating highly specific anti-TF antibodies and because of their nature as IgM isotypes with comparably lower intrinsic affinities of single binding domains, TF-specific antibodies were not further developed so far. Further, some anti-TF-Ag antibodies are not clinically useful because they cause undesirable proliferation of tumor cells. Also WO2006/012626 describes the therapeutic use of anti-TF antigen antibodies. Binding of TF-specific Abs has been shown to inhibit the proliferation of tumour cells (Jeschke, et. al. 2006).
Furthermore, there were also attempts to develop vaccines based on Thomsen-Friedenreich. Most of them focused on the induction of antibody responses. Eg. Livingston and Lloyd (2000) used non-natural TF-conjugates, wherein synthetic TF was randomly coupled to KLH. This conjugates raised a humoral immune response against synthetic TF but not against TF on natural ligands (Adluri et al, 1995). They were thus not TF specific as they would not recognize TF on a tumor structure.
Springer and Desai used vaccination with a T/Tn vaccine composed of types 0 and MN red blood cell derived glycoproteins which resulted in improved breast cancer patient survival although only small amounts of IgM were made. However, IgM represents a less mature immune response and many previous studies relating to antibodies to TF-Ag involve IgM antibodies, therefore more pronounced highly TF specific immunoresponses would be needed and preferably an IgG response.
Few reports are known which describe microorganisms supposedly positive for TF. E.g. Springer et al. (Brit. J Haematol, 1981, 47, 453-460.Transfusion 1979, vol. 19, no. 3 pp. 233-249) report on an aerobic microorganism (Ecoli O86) which can generate a polyclonal antibody response in chickens and humans which might also recognize TF on human erythrocytes. Springer used adsorption of anti-T and hemagglutination assays with sialidase-treated T erythrocytes in order to determine roughly the specificity of the immune response. However, sialidase-treatment of human erythrocytes results in demasking of several carbohydrate epitopes, among them but not exclusively TF. Therefore, the reaction tested by Springer does not show a specificity for TF due to cross-reactivities. A respective non-specific microorganism has only a limited suitability as a vaccine due to its unspecificity as it would not raise a strong immune response which is specifically directed against TF but against similar TF-like structures and hence potentially also increasingly against non-tumor tissues or cells of the body.
Due to the complexity and species specificity of the glycosylation machinery no immunotherapy based on Core-1 is available yet to cancer patients. Even more important, there is no agent available to patients which can prevent the development of Core-1 positive tumors.
Conventional therapies usually start after tumor diagnosis, when tumors are often well established and difficult to treat. Therefore, aggressive therapies with severe side effects (chemotherapy, radiotherapy, surgery) are used to free the patients from tumor bulk. Immunotherapeutical options are mainly applied in the adjuvant setting with minimal residual disease.
The object of the present invention is to provide means for treatment or prevention of Core-1 positive tumors and gastrointestinal disorders as well as suitable tools for obtaining respective means.